Copter sometimes stuck at waypoints

Hello all,

Quadcopter running PX4 1.5.5 with LPE sometimes get stuck at waypoints. Here are the logs for normal, successful missions, which have ended successfully:

I had to manually get the copter to bring it back to its home in both of these missions. Here are some logs for unsuccessful missions. In the first log, the copter is stuck at the first waypoint. And in the second, the copter is stuck at the second waypoint. Please take a look!

Could this be related to some altitude problem? My NAV_MC_ALT_RAD parameter is 3.0
and NAV_ACC_RAD is 3.2